Lignocellulosic biomass includes herbaceous crops, hardwoods, and softwoods such as switchgrass, hybrid poplar, and pine respectively. Such biomass materials are used as precursors for chemicals, polymers, fibers, fuels, and the like. Lignin may be isolated from the biomass and used to produce a multitude of products and intermediates. Products may include, but are not limited to, resins, foams, fuels, dyes, dispersants, films, packaging materials, electrochemical devices, and structural and non-structural fibers.
Hemicelluloses are another component of lignocellulosic biomass. Hemicelluloses are important to the paper industry. In chemical wood pulps, hemicellulose is needed for satisfactory pulp quality. Hemicelluloses aid the swelling of the pulp, the bonding of the fibers, the bursting strength, tensile strength, tear resistance, folding endurance, opacity, and specific surface of the pulp sheet. Hemicelluloses also serve as a sugar source for yeasts, and can be used for a raw material in the production of furfural and ethyl alcohol. Hemicellulose can also be used to make films, surfactants, fuels, and other chemicals.
An additional important component of lignocellulosic biomass is cellulose. Cellulose is used in a wide variety of applications, including but not limited to nanomaterials, pharmaceuticals, fuels, chemicals, polymers, fibers, paper, and the like. About a third of the world's production of purified cellulose is used as the base material for a number of water-soluble derivatives with pre-designed and wide-ranging properties dependent on the groups involved and the degree of derivatization. For example, cellulose is a source chemical for making cellulose acetate. Hydroxypropyl-methylcellulose and methylcellulose may be used in gluten-free bakery products as gluten substitutes. Hydroxypropyl cellulose is a water-soluble thickener, emulsifier and film-former often used in tablet coating. Another important derivative of cellulose is carboxymethylcellulose which may be used as to make additives for foods, pharmaceuticals, and the like.
A minor, but important component of lignocellulosic biomass is extractives that include non-structural phenolic compounds, fatty acids, glycerides, waxes, terpenes, and terpenoids. Such compounds may be useful, for example, for making biopesticides and pharmaceuticals.
Until now, industries have focused on optimizing only one or two components from lignocellulosic biomass without attempting to isolate and purify all of the components listed above. In other words, processes directed to removing and isolating lignin have generally been detrimental to at least one of the three major components of the biomass, rendering such components minimally valuable. Accordingly, what is needed is an integrated process for isolating and purifying all of the components of lignocellulosic biomass to provide purified products in high yield.
In view of the foregoing, an embodiment of the disclosure provides an integrated process for treating lignocellulosic biomass in order to separate the biomass into its component parts. The process includes the steps of: a) contacting the lignocellulosic biomass with a first solvent, for a period of time and at a first temperature at a severity in the range of about 2 to about 4 to remove extractive components and a portion of ash from the biomass. The biomass from step (a) is then contacted with a second solvent, and optional catalyst, at a second temperature at a severity in the range of about 1 to 5 to remove hemicelluloses and additional ash from the biomass. The biomass from step (b) is separated into a lignin product and a cellulose product by contacting the biomass from step (b) with a third solvent at a severity in the range of about 1.5 to 5 to provide a black liquor and a solid fraction containing cellulose.
In another embodiment, there is provided a comprehensive process for treating lignocellulosic biomass in order to separate the biomass into its component parts. The process includes: a) contacting the lignocellulosic biomass with a first solvent for a period of time and at a first temperature at a severity in the range of about 2 to about 4 to remove extractive components and a portion of ash from the biomass. The biomass from step (a) is then separated into a lignin product and a cellulose product by contacting the biomass from step (a) with a third solvent at a severity in the range of about 1.5 to 5 to provide a black liquor and a solid fraction containing cellulose.
A further embodiment of the disclosure provides a comprehensive process for treating lignocellulosic biomass in order to separate the biomass into its component parts. The process includes: a) contacting the lignocellulosic biomass with a first solvent with or without a catalyst at a temperature at a severity in the range of about 1 to 5 to remove hemicelluloses and ash from the biomass. The biomass from step (a) is then separated into a lignin product and a cellulose product by contacting the biomass from step (a) with a third solvent at a severity in the range of about 1.5 to 5 to provide a black liquor and a solid fraction containing cellulose.
An advantage of the claimed process is that individual components of the lignocellulosic biomass may be separated into lignin, cellulose, hemicelluloses, and extractives with high yield and high targeted properties. The high yield and high purity of the components from the lignocellulosic biomass enables the conversion of the components into chemicals, products, and fuels with minimal additional processing. Accordingly, the waste materials from the lignocellulosic biomass components are greatly reduced. For example, the high purity lignin may be converted into carbon fibers without additional extensive lignin treatment and purification steps.